Rotary drilling device



March 5, 1968 c. ASMANES 3,371,558

ROTARY DRILLING DEVICE Filed Feb. 15. 1966 I 2 Sheets-Sheet l INVENTOR.

FT. 1 Char/es Asmanes ATTORNEY.

MQQW/W March 5, 1968 c. ASMANES 3,371,558

ROTARY DRILLING DEVICE Filed Feb. 15. 1966 2 Sheets-Sheet 2 s m m m M m m iw% M w m s L M c Y B ATTORNEX United States Patent Otlice 3,371,553 Patented Mar. 5, 1968 3,371,558 ROTARY DRILLING DEVICE Charles Asmanes, Oak Ridge, Tenn., assignor to the United States of America as represented .by the United States Atomic Energy Commission Filed Feb. 15, 1966, Ser. No. 529,179 Claims. (CI. 77-29) The invention described herein was made in the course of, or under, a contract with the US. Atomic Energy Commission. This invention relates generally to drilling devices, and more specifically to a high-speed rotary drilling device particularly suitable for drilling small-diameter holes.

Commercially available drilling systems capable of providing perforations or holes of small cross-sectional dimensions such as those occurring in a diameter range of about 0.002 to about 0.030 of an inch suffer several shortcomings or drawbacks which tend to render them somewhat incapable for overcoming some of the problems that may be present during such drilling. Perhaps one of the more significant problems encountered during the drilling of small-diameter or miniature holes in about the above-noted size range is drill-bit wobble, i.e., drill-bit rotation about an axis diiferent from the normal axis of the drill bit. Drill-bit wobble is an undesirable operating condition that frequently causes the drill 'bit to grab the workpiece and break. Also, drill-bit wobble may be responsible for the drilling of a hole which may be sufficiently oversized to damage or otherwise render the hole unsuitable for its intended purpose. In previous drilling devices, the drill bit is usually affixed to a suitable drillbit rotating mechanism by a chuck arrangement. The proper mounting of a drill bit in such a retaining arrangement involves the practicing of a very difficult procedure which may or may not result in an essentially wobblefree drill-bit mounting.

Another of the more significant problems encountered during the drilling of miniature holes is due to the mechanism used for advancing the drill bit into the workpiece. For example, previous drilling systems normally use an intricate, manually operable lever assembly to provide control over drill-bit advancement. Frequently, such levers are counterbalanced with carefully positioned Weights to increase control sensitivity for the operator. However, this system of levers, counterbalanced or othervw'se, has not been found to provide the operator with a suitable mechanism for enabling him to exercise adequate control over drill-bit advancement. For example, when using such previous drill-bit advancing mechanisms, it is very difiicult for the operator to determine various stages of drill-bit dullness during a drilling operation since the drill-bit advancing mechanism is not sufficiently sensitive to such conditions for permitting desired control thereover. Thus, if the drill bit does not appear to be advancing into the workpiece, the operator cannot, with any degree of accuracy, determine whether he should exchange drill bits because of drill-bit dullness or apply additional drill-bit advancing force. Frequently, the placement of such additional force on a drill bit of small diameter will cause it to break. The removal of a broken drill bit from a workpiece often requires a considerable amount of time during which the drilling operation must be suspended or otherwise interrupted.

The present invention aims to obviate or substantially minimize the above-mentioned and other shortcomings or drawbacks by providing a new and improved drilling device particularly suitable for drilling small-diameter holes. This drilling device utilizes a novel drill-bit retaining arrangement which is capable of eliminating or substantially minimizing drill-bit wobble. Further, the drill bit is driven by a novel drive system utilizing a frictional engagement which provides for substantially greater drill-bit speeds than attainable with previous mechanically driven drilling systems. Manual control of drill-bit advancement or retraction is achieved in a highly precise manner by selectively varying the direction of application of the drillbit driving force supplied by the frictional engagement so as to simultaneously rotate the drill bit and effect movement of the latter in a direction parallel to its axis of rotation.

An object of the present invention is to provide a new and improved drilling device for drilling holes in a diameter range of about 0.002 to about 0.030 of an inch or bigger.

Another object of the present invention is to provide a new and improved drill-bit mounting arrangement for effectively eliminating or minimizing drill-bit wobble.

Another object of the present invention is to provide a drill-bit driving system for maintaining the drill bit in a desired Orientation by a frictional engagement and for imparting higher rotational speeds to the drill bit than previously attainable.

A further object of the present invention is to provide a manual control system which may be readily and accurately utilized to precisely regulate drill-bit advancement and retraction during drilling operations.

A still further object of the present invention is to utilize an integrated drill-bit driving system and control system for providing accurate drill-bit advancement and retraction.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or Will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description. The preferred embodiment illustrated is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is chosen and described in order to best explain the principles of the invention and their application in practical use to thereby enable others skilled in the art to best utilize the invention in various embodiments and modifications as are best adapted to the particular use contemplated.

In the accompanying drawings:

FIG. 1 is a perspective view showing a preferred form of a drilling device embodying the novel features of the present invention;

FIG. 2 is a fragmentary view, partly broken away, of the FIG. 1 device showing details of the novel drill-bit mounting, driving, and positioning arrangement of the present invention;

FIG. 3 is a fragmentary sectional view taken generally along line 3-3 of FIG. 2 and showing in greater detail the drill-bit mounting and driving arrangement; and

FIG. 4 is a fragmentary view of the FIG. 1 device showing a portion of the manually operable, mechanical control for regulating drill bit advancement or retraction.

Described generally and with reference to the accompanying drawings, the drilling device of the present invention, as generally indicated by numeral 10, provides a unique system for driving and mounting a drill bit. The drill bit 12, which may be of any suitable commercially available type such as one having a fluted shaft of uniform diameter or one having a shank portion of a greater diameter than the drilling portion, is shown being held or carried in an operative position in the drilling device 10 due to its confinement between an open-faced bearing element 3 14 and a rotatable disc or wheel 16. This wheel 16 continually exerts a force against the drill bit 12 to maintain it in a desired abutting relationship with the bearing element 14 and is disposed in a plane normal or perpendicular to the rotational axis of the drill bit such that upon rotation of the wheel the frictional engagement of the latter with the drill bit effects rotation of the drill bit.

In order to provide relative movement of the drill bit 12 with respect to the bearing element 14 in a direction parallel to the axis of the drill bit, the wheel 16 is selectively tilted about its axis of rotation from the position shown so as to direct a portion of the rotational force upon the drill bit along the rotational axis of the latter. Thus, with this rotational force being partially diverted from a plane perpendicular to the drill bit axis toward a plane parallel with the drill-bit axis, the driving force imposed by the rotating wheel 16 simultaneously rotates the drill bit while moving the latter in the desired direction.

Described in greater detail the drilling device is shown for purposes of description in the form of a drill press which may comprise a base 17 having secured thereto at spaced-apart locations an upwardly projecting flange 18 and a suitable pedestal 20 for supporting a workpiece (not shown). A cross-arm 21 may be secured to the flange 18 adjacent the uppermost end thereof and laterally extend therefrom so as to terminate in a location generally over the pedestal 20. This free end of the cross-arm 21 may be provided with a relatively thick portion or block 23 that is slotted or grooved for receiving and maintaining a drill-bit holder 24 in a desired vertical orientation. The drill-bit holder 24 is preferably secured to the block 23 or flange 18 by readily removable means such as the strap-and-bolting arrangement generally shown in FIG. 1 at 25. The drill-bit holder 24 is preferably of an elongate configuration and provided with a throughgoing passageway 26 for receiving a drill bit 12. This passageway 26 may include an upper section, as shown, of greater diameter than the lower passageway section for receiving a compression spring assembly 27 which may be used to continually urge the drill bit 12 toward the workpiece (not shown). The constant bias provided by this spring assembly 27 assures that any bounce-back or reluctance of the drill bit to advance toward the workpiece will be minimal. This bias feature is particularly advantageous when using drill bits of relatively large diameters in that the bias of the spring aids the wheel in urging the drill bit into the workpiece, thus avoiding positioning of the wheel in an undesirable rotational plane for effecting drill-bit movement. Also, if desired, the spring assembly 27 may be removed so as to permit the use of relatively long drill bits in the drilling device. The drill-bit holder 24 is preferably carried by the cross-arm 21 in such a manner as to position the lowermost end of the drill-bit holder adjacent to and in the projection of the rotational plane of the friction wheel 16, as shown. This lowermost end of the drill-bit holder may be partially cut-away on the side thereof disposed toward the friction wheel 16 to expose the passageway 26 at a location above the wheel 16 and provide an appendage for carrying the bearing element 14 in the projection of the rotational plane of the wheel 16.

Inasmuch as the drill bit 12 is maintained in an abutting relationship against the bearing element 14 during drilling operations, it is preferable that the bearing element 14 be made of a material capable of providing minimal frictional forces due to relative movement between the drill bit and the bearing element. A bearing element formed from a hard substance such as sapphire or any other equivalent material from a friction standpoint may be satisfactorily used. The bearing element 14 is preferably of such a size as to contact a considerable length of the drill bit 12, e.g., about one inch, to assure adequate support of the drill bit while essentially eliminating any drill-bit wobble. With a bearing element of about this length, the surface area of the drill bit contacted by the bearing element is substantially greater than and overlaps the surface area of the drill bit in contact with the wheel 16. This relationship of surface areas or lengths of the drill bit contacted by the drill bit and the wheel provides a drill-bit mounting which assures maximum drill bit support while facilitating the rotation and axial movement of the latter. Also, the bearing element is preferably provided with a vertically extending and inwardly converging slot or groove 28 in registry with the passageway 26 for providing a suitable drill-bit receiving receptacle in the bearing element. However, this groove 28 should be of such dimensions that, when the drill bit 12 is within the groove 28, at least a portion of the drill-bit 12 cross section projects from the bearing surface to provide a contacting surface for the wheel 16 (FIG. 3).

While the bearing element is shown formed from a single piece of bearing material with the vertically extending groove 28 in a surface thereof, it will appear clear that the bearing element may be formed from two cylindrical rods of the bearing material with these rods being disposed in a side-by-side relationship such that a groove corresponding to groove 28 is naturally formed therebetween.

The bearing element 14 may be mounted on the drillbit holder by using a bracket assembly 29 which has a lip portion thereof disposed under the bearing element.

The cross-arm 21 may be provided with a depending portion 30 which preferably projects from the underside of the cross-arm 21, as shown, and is provided with a throughgoing passageway for receiving in a rotatable manner an elongated shaft 31. This shaft 31 is preferably carried by the depending portion in such a manner as to be disposed in a plane parallel to the cross-arm 21.

The shaft 31 is used to carry the wheel 16 for positioning the wheel in a desired working relationship with the drill bit 12 and for providing a means to selectively change or vary the rotational plane of the wheel 16 for effecting drill-bit movement. In order to provide a suitable structure for mounting the wheel 16 to the shaft 31, the latter may be provided with an extension in the form of an arm 32 having an offset configuration. This arm 32, which may be secured to the shaft 31 in any suitable manner, e.g., a bolting arrangement, may be provided adjacent the free end thereof with a flanged hub or pin 33 laterally projecting from the arm 33 as to be disposed in a plane parallel to the axis of the drill bit. The wheel 16 may be rotatably mounted on this pin 33 by utilizing a suitable bearing arrangement, such as, for example, a roller hearing assembly 34, operatively disposed between the pin 33 and the wheel.

The wheel 16 may comprise a pair of integrally formed and adjacently disposed annular discoid-like portions of different diameters. The larger of these discoid-like wheel portions, as indicated by the reference character 35, is disposed in such a location by the shaft 31 with respect to the bearing element 14 that marginal or peripheral edges or surfaces of the wheel portion 35 are maintained in a close spatial relationship with the center of the bearing element 14 irrespective of the rotational plane of the wheel 16.

The spacing between the bearing element and the peripheral surface of the wheel portion 35 is variable for permitting the use of drill bits of different diametral sizes. However, regardless of the diametral size of the particular drill bit being used, the wheel exerts a continuous force against the drill bit to maintain it in abutting relationship with the bearing element 14. To provide this continuously applied force against the drill bit, a suitable spring means, such as, for example, a helically wound compression spring 36, may be disposed about the shaft 31 intermediate the wheel 16 and the depending portion 30 on the cross-arm 21. The spring has one end thereof abutting against the depending portion so as to continually urge the wheel 16 toward the bearing element.

With a drill bit positioned between the wheel and the bearing element, the wheel 16 imposes a force in a continuous manner against the drill bit to maintain it in an abutting relationship with the bearing element 14. To rotate the drill bit 12, the peripheral surfaces of the wheel portion 35 contacting the drill bit 12 may be provided with a suitable surface or surface material capable of providing a frictional coupling or engagement with the drill bit 12 to facilitate rotation thereof while minimizing slippage between the wheel and drill bit. For example, a suitable friction surface may be provided by placing a layer 37 of polyvinyl chloride about the periphery of the wheel portion.

The rotational speed of the drill bit 12 is determined by the diametral relationship of the wheel portion 35 to the drill bit 12. Thus, with a wheel 16 having a diameter many times greater than the diameter of the drill bit, extremely high rotational speeds may be enjoyed by the drill bit. For example, rotational speeds of the drill hit up to about 60,000 revolutions per minute (r.p.m.) have been achieved without difiiculty.

The discoid-like wheel portion having the smaller diameter, as indicated by the reference numeral 38, may be provided with a circumferentially extending groove 39 for receiving a belt 40 which, in turn, is driven to effect rotation of the wheel. This belt 40 may be made of any suitable well known belt material.

In order to drive the belt 40 to effect wheel rotation, the belt 40 may be afiixed to a pulley on the rotatable shaft 41 of a suitable electric motor 42 (FIG. 4). This motor 42 may be carried by the shaft 31 to maintain the motor 42 in a satisfactory belt-driving position irrespective of the rotational plane of the wheel 16. A suitable mounting of the motor 42 to the shaft 31 may be provided by securing the motor 42 to a plate 44 and, in turn, afiixing the plate 44 to the shaft through the intermediation of a suitable arm-like segment 45. A suitable motorspeed regulating device, e.g., a rheostat 46, may also be mounted on the plate 44 for providing readily available means for changing motor speeds.

As briefly mentioned above, movement of the drill bit toward or away from a workpiece on pedestal 20 is achieved by tilting the wheel 16 for redirecting part of the drill-bit rotational forces supplied by the wheel in a direction toward the parallel of the drill-bit rotational axis. To accomplish this tilting movement of the wheel 16 in a controlled manner for providing precise movements of the drill bit 12, the shaft 31 is rotated in depending portion 30 in the cross-arm 29. This rotation of shaft 31 may be achieved by fixedly securing .a lever arm 47 through the intermediation of a sleeve-like structure 51 to the shaft 31 in any suitablelocation, such as, for example, adjacent the wheel 16 as shown in FIGS. 1 and 2.

To facilitate the manual movement of the lever arm 47 1n a desired manner, the spring 36 may be secured to the depending portion 30 and the sleeve-like structure 51 so as to provide a slight assistance to shaft rotation. The sensitive control over manual movement of the shaft 31 may be enhanced by attaching a weight 52 to the shaft I for counterbalancing the lever arm 47. Also, the lever arm may be provided with a weight 53 which may be moved to varlous positions on the shaft of the lever arm 47 for providing a means for controlling arm position, for offsetting the weight of the motor and rheostat, and for varying the effect the spring 36 has upon arm movement.

In order to regulate and control manual movement of the lever arm 47 which, in turn, determines by the extent of its movement the relative force applied by the wheel 16 against the drill 'bit 12 for moving the latter in a direction parallel to its axis, a selectively adjustable mechanical stop may be used to limit lever arm movement. A suitable mechanical stop may be fabricated by providing the plate 44 with an arcuately shaped aperture or slot 54 (FIG. 4) for receiving a pin 55 secured to the cross-arm 21. When the shaft 31 is rotated, relative movement occurs between the pin 55 and slot 54. The extent of this movement may be regulated by utilizing selectively adjustable screw-like members 57 and 58 to interrupt the slot for preventing further shaft rotation after tilting of the wheel 16 has been achieved in a desired direction. These screw-like members 57 and 58 may be threadedly received in suitable bores in the plate 44. Using a mechanical stop of the type described also provides an operator with a mechanism for assuring that the same axial force is applied on the drill bit during subsequent drilling operations of a similar nature.

In addition to or in lieu of the mechanical stopfor regulating rotation of the shaft 31, a visual control may be utilized. For example, a dial 59 carrying suitable indicia may be used to depict the extent or degree and direction of the rotation or tilting of the rotational plane of the wheel 16. A pointer 60 secured to the shaft 31 may be used to indicate the extent of wheel tilting on the dial.

By using a calibrated dial 59, the operator may be provided with a desirable control feature for assuring the attainment of drillings in workpieces of various materials without suffering problems, e.g., the inability of accurately determining drill-bit dullness, drilling pressure, etc., frequently encountered by using previous drilling systems. For example, in a typical drilling operation employing the drilling device of the present invention, the operator may provide a drilling with minimal difficulty by following drilling instructions predetermined for the particular drilling. Such instructions may read as follows: drill 10 minutes employing a dial indication of 5 degrees. Change to a new drill bit. Drill 5 minutes employing a dial indication of 5 degrees. Withdraw drill bit. As the result of properly executing the drilling by following such instructions, drill-bit dullness or other problems will not be troublesome since, with a workpiece of a particular metal or metals, it is readily determinable beforehand that the drill bit having X units of force applied along the drill-bit axis will become dull after a certain drilling time. Further, such practices may be used to determine beforehand what the approximate hole depth will be after drilling with one or more drill bits experiencing the same or different forces along the drill-bit axes for a selected time period.

In order to mount a drill bit 12 between the wheel 16 and the bearing element 14, several techniques may be employed. For example, the wheel 16 may be moved away from the bearing element 14 by using the counterweight 52 as a lever arm to slide the shaft 31 in the depending portion 30 of cross-arm 21, thus facilitating the placing of a drill bit in the bearing element groove from either the upper or lower end thereof or from the side of the bearing element. Of, if desired, the uppermost or lowermost end of the drill bit 12 may be positioned in the bearing element groove so as to contact the wheel 16 and then the wheel tilted in an appropriate plane and driven to pull the drill bit into the space between the wheel and the bearing element.

Inasmuch as the force imposed upon the drill bit by the spring-loaded wheel 16 varies with drill bits of different diameters, it becomes desirable to use a mechanism or means to assure that this applied force is neither excessive as to bind the drill bit against the bearing element nor insufficient as to cause excessive slippage due to an inadequate frictional contact. A mechanism found to be satisfactory for selectively adjusting this applied force is afforded by providing the arm 45 attached to the plate 44 and the shaft 31 with a threaded throughgoing passageway in registry with the counterweight 52. A knurled bolt 61 may be disposed in this passageway and a'but against the counterweight 52 so as to effect shaft and wheel movement away from the bearing element by merely tuming the bolt 61 inwardly into the arm passageway.

While the present invention is shown in the form of a drill press, it will appear obvious that the drilling devic of the present invention may be used with other systems. For example, by removing the cross-arm 21 from the flange 18, the drilling device may be used with a lathe or the like by utilizing a chucking lug such as shown on cross-arm 21 at 62.

It will be seen that the present invention sets forth a new and improved drilling device which is capable of providing drillings in a highly precise manner at a cost substantially less than previously enjoyed due to substantially minimizing or eliminating drilling problems such as drill-bit breakage, drill-bit wobble, incorrect drilling depths, etc. Further, the drilling device of the present invention is capable of rotating drill bits through an infinite range of speeds which may vary from about 300 r.p.m. or less to about 60,000 r.p.m. depending on the material of the workpiece, which may be as soft as gold or as hard or tungsten. Also, the present drilling device has been found to be highly satisfactory for drilling holes in laminated structures made up of metals or materials of ditferent hardnesses.

As various changes may be made in the form, construction, and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A high-speed rotary drilling device of the character described, comprising a housing, bearing means carried by said housing for supporting a drill bit having an axis of rotation, rotatable means having a plane of rotation disposed generally perpendicular to said axis and spaced from said bearing means, said rotatable means being engageable with said drill bit when the latter is in said bearing means for maintaining said drill bit in an abutting relationship with said bearing means and for imparting a rotational force to said drill bit to effect rotation of the latter about said axis, and means coupled to said rotatable means for selectively positioning the plane of rotation of the rotatable means for redirecting a portion of the rotational force from a plane normal to said axis toward a plane parallel with said axis to effect relative movement of said drill bit with respect to said bearing means in a direction parallel to said axis.

2. A high-speed rotary drilling device as claimed in claim 1, wherein said bearing means comprises an elongate structure overlapping said rotatable means for contacting surface portions of said drill bit corresponding to a greater length of said drill bit than surface portions of the latter engaged by said rotatable means, said elongate structure consists of a material having properties exhibiting minimal generation of frictional forces when said drill bit abutting thereagainst is subjected to relative movement with respect thereto, and wherein only a portion of the drill bit girth is maintained in said abutting relationship with said elongate structure.

3. A high-speed rotary drilling device as claimed in claim 1, wherein said rotatable means comprises a wheel having a diameter substantially greater than the diameter of said drill bit, peripheral surfaces of said wheel provide the engagement with said drill bit, and wherein the engagement with said drill bit is a frictional engagement provided by forming at least the peripheral surfaces of said wheel of a material capable of imparting with minimal slippage the rotational forces from said wheel to said drill bit.

4. A high-speed rotary drilling device as claimed in claim 3, wherein said bearing means comprises an elongate structure having a groove therein disposed parallel to said axis for receiving said drill bit with side walls of said structure defining said groove providing said abutting relationship, said groove envelops a cross-sectional area of said drill bit less than the total cross-sectional area of the latter for maintaining a portion of said drill bit outside of said groove, said elongate structure consists of a material having properties exhibiting minimal generation of frictional forces when said drill bit is subjected to relative movement with respect thereto, and wherein said wheel is engageable with surface portions of said drill bit maintained outside of said groove and overlapped by surface portions of said drill bit abutting against said bearing means.

5. A high-speed rotary drilling device as claimed in claim 4, wherein a drill-bit holder is secured to said housing for carrying said bearing means in a projection of the rotational plane of said wheel, said holder has a passageway thcrethrough in registry with said groove for receiving said drill bit, and wherein bias means are within said passageway for continually urging movement of said drill bit when in contact therewith.

6. A high-speed rotary drilling device as claimed in claim 3, wherein said means coupled to said rotatable means for selectively positioning the rotational plane thereof comprises a shaft coupled to said wheel and rotatably carried by said housing, and wherein spring means continually urge said wheel toward said bearing means to effect and maintain the engagement with said drill bit.

7. A high-speed rotary drilling device as claimed in claim 6, wherein arm means are coupled to said shaft for facilitating rotation thereof, and wherein a weight is carried by said shaft for counterbalancing said arm means.

8. A high-speed rotary drilling device as claimed in claim 6, wherein selectively adjustable means are connected to said shaft for controlling the extent of rotation thereof.

9. A high-speed rotary drilling device as claimed in claim 8, wherein said selectively adjustable means comprise a plate connected to said shaft and rotatable therewith and having an elongated aperture therein for receiving a relatively stationary projection therein, and wherein means are carried by said plate and relatively movable with respect thereto for selectively varying the effective length of said aperture to regulate relative movement between said plate and the projection.

10. A highspeed rotary drilling device as claimed in claim 9, wherein drive means are carried by said shaft and coupled to a portion of said wheel for effecting rotationof the latter.

References Cited UNITED STATES PATENTS FRANCIS S. HUSAR, Primary Examiner. 

1. A HIGH-SPEED ROTARY DRILLING DEVICE OF THE CHARACTER DESCRIBED, COMPRISING A HOUSING, BEARING MEANS CARRIED BY SAID HOUSING FOR SUPPORTING A DRILL BIT HAVING AN AXIS OF ROTATION, ROTATABLE MEANS HAVING A PLANE OF ROTATION DISPOSED GENERALLY PERPENDICULAR TO SAID AXIS AND SPACED FROM SAID BEARING MEANS, SAID ROTATBLE MEANS BEING ENGAGEABLE WITH SAID DRILL BIT WHEN THE LATTER IS IN SAID BEARING MEANS FOR MAINTAINING SAID DRILL BIT IN AN ABUTTING RELATIONSHIP WITH SAID BEARING MEANS AND FOR IMPARTING A ROTATIONAL FORCE TO SAID DRILL BIT TO EFFECT ROTATION OF THE LATTER ABOUT SAID AXIS, AND MEANS COUPLED TO SAID ROTATABLE MEANS FOR SELECTIVELY POSITIONING THE PLANE OF ROTATION OF THE ROTATABLE MEANS FOR REDIRECTING A PORTION OF THE ROTATIONAL FORCE FROM A PLANE NORMAL TO SAID AXIS TOWARD A PLANE PARALLEL WITH SAID AXIS TO EFFECT RELATIVE MOVEMENT OF SAID DRILL BIT WITH RESPECT TO SAID BEARING MEANS IN A DIRECTION PARALLEL TO SAID AXIS. 